Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers and semiconductive layers of material over a semiconductor substrate or workpiece, and patterning the various layers using lithography to form circuit components and elements thereon.
Isolation regions are used in semiconductor devices to electrically isolate active areas and electrical components from other active areas and components. Isolation regions are typically formed by forming holes or trenches in a semiconductor workpiece, and filling the holes with an insulating material.
In some semiconductor devices, trenches for isolation regions may form in a retrograde shape, being wider at lower portions than at upper portions of the trenches. When these retrograde trenches are filled with an insulating material, air gaps or voids tend to form in the larger, lower portion of the trenches, which results in a degradation of the isolation properties of the isolation regions in some semiconductor applications.
Thus, what are needed in the art are improved methods of filling retrograde isolation regions and structures thereof.